Most products have limited useful lifetimes, which generally span from when a product is new (or ready to be used) to when it fails to function properly and, consequently, may be less useful than when it was new. Thus, products go through several stages during their lifetimes, including what may be characterized as a beginning, a middle and an end. The lifetime of a product may be generally understood with reference to the nature of the product. For some products, their lifetime may be determined mostly by the passage of time. A piece of fruit, for example, generally has a lifetime that comes to an end when the piece of fruit becomes overripe and is no longer palatable, which happens with the passage of time. For some products, their lifetime may be determined primarily by the amount of use of the product. A traditional wooden pencil, for example, reaches the end of its lifetime after it is used and sharpened so many times that the wooden cylinder surrounding the graphite core cannot be sharpened any further, or until the wooden cylinder is reduced to a size where the pencil is no longer desirable for use. And for some products, their lifetime may be determined mostly by a combination of the passage of time and the amount of use of the product. A rubber bicycle tire, for example, may degrade and dry out over time and may be worn down by use.
Effective use of a product generally includes using the product during its useful lifetime, and discontinuing use of the product once the product reaches the end of its useful lifetime. Determining what stage of its lifetime a product is in may be difficult for a potential user, especially for a product that doesn't provide readily apparent indications about where it is along its useful life.
In some circumstances, a change in the user of a product may influence the product's useful lifetime. For example, a change in a user's health status might influence whether a particular product is still useful to the user. In addition, a change in a user's preferences might influence whether the user perceives the product as useful.
Mattresses provide an example of a product whose useful lifetime may be influenced by its age, use, and a user's preferences. A mattress typically includes a cover made of durable upholstery which may be partially or entirely covered by a mattress pad and/or sheets while the mattress is being used. Because of this covering, a superficial visual inspection of a mattress surface may not reveal the amount of use the mattress has seen or the age of the mattress, which may be factors in determining its useful life. A potential purchaser of the mattress may be deceived or misinformed regarding the remainder of the useful life of the mattress. Moreover, some mattress owners may find it difficult to recall exactly when the mattress was purchased or how long or how often the mattress has been used. The amount of time a mattress owner has owned a mattress may be relevant, as mattress owners may prefer different mattress qualities (such as stiffness) at different stages in their lives. Thus, mattresses in particular, and products generally present problems in terms of understanding how far along (or how far beyond) they are in their useful lifetime.
Thus, a need exists in the art for apparatus that may assist product owners with understanding when a product is nearing the end, or has been used past the end of, its useful lifetime. Such apparatus may have application with respect to mattresses.